Conventionally, a wireless transceiver for use in a portable device of Smart Key system (registered trademark) is carried by a user, and communicates with a station disposed on a vehicle when the user enters into the vehicle. The transceiver in the portable device of the Smart Key system allows the user to unlock a door of the vehicle, to start an engine or to perform other operation when the transceiver is carried by the user.
The transceiver includes a circuit board for mounting circuit parts and a battery as a power source in a resin case. The transceiver also includes a mechanical key stored therein for use in an emergency such as battery rundown, breakdown on the transceiver, or the like. The mechanical key is accepted in a hollow space in the resin case. In case of an emergency, the user pulls out the mechanical key from the hollow space of the resin case, and uses the key for unlocking the door or for other purposes.
However, the transceiver uses a more complicated and sophisticated system that tends to use an increased number of parts, while a volume of the transceiver body is required to be much more smaller in order to be conveniently carried by the user. That is, the transceiver in a thin card shape is particularly preferred.
In this case, dimension of the mechanical key is approximately 2 mm in thickness, and this allows the resin case on both sides of the key (i.e., the portion around the hollow space) only to be in a thickness of 0.5 mm when a total thickness of the transceiver is 3 mm. Therefore, physical strength of the transceiver at the hollow space portion becomes not necessarily sufficient.
That is, the transceiver may be broken in case of falling from a certain height because of the insufficient strength of the hollow space portion for an impact caused by the weight of the mechanical key (approximately 5 gram).
This kind of problem is commonly found in the transceiver for use in other type of keys, such as a key for opening/closing an office door, a key for operating a testing device or the like beside the transceiver for the Smart Key system.